1. Field of the Invention
The present invention relates to a friction hinge device, and more particularly to an improved clip type friction hinge device which can be conveniently assembled and can easily adjust a torque.
2. Description of the Related Art
A friction hinge device is a very useful device for maintaining an object at a predetermined position or at a predetermined angle. For example, it is used to maintain a display of a notebook computer at a predetermined angle for a main body thereof or to properly adjust and maintain the screen angle of an LCD monitor. That is, in a notebook computer, the friction hinge device combines a cover in which a display is integrated to a main body so that the display can be opened/closed up and down. When the cover is opened, the friction hinge device serves to maintain the cover at a proper angle for the main body by the pressure of the spring and clip therein. In addition, the friction device generates a dynamic torque due to the friction when an object like a cover of a notebook computer is moved or rotated, thus restraining a rapid operation of the object and buffering the shock.
Representative modes presently used for such a friction hinge device are a wrap spring mode, an axial disk compression mode, a roll pin mode and a clip spring mode, and so on.
Such a friction hinge device is advantageous in its own way. However, most of the devices cannot be manufactured to a structure proper to a recent trend pursuing the miniaturization/thinness of products, or even though it can be manufactured in that way, it is complicated to manufacture it and the durability thereof rapidly drops in the case that high torque should be maintained. Therefore, to solve these problems, a friction hinge device of torsion spring mode has been recently developed.
The friction hinge device of torsion spring mode is constructed to adjust both the friction area and the pressure of a spring and to generate a frictional force of a constant size.
FIG. 1 shows a conventional friction hinge device of a torsion spring mode as described above.
As shown in FIG. 1, the friction hinge device has a housing 10, a rotary axis 20 and a torsion spring 30.
The housing 10 has an axial hole 10a and a fixing slot 10b formed at the lower portion of the axial hole 10a.
The rotary axis 20 has a first axis part 20a which is inserted to the axial hole 10a of the housing 10, a second axis part 20b connected to the end of the first axis part 20a and a fixing part 20c connected to the second axis part 20b and extended to the opposite direction of the first axis part 20a. The first and second axis parts 20a and 20b and the fixing part 20c may be separately or unitedly formed according to the conditions in manufacturing and assembling. A hole for screw 20d is formed at the fixing part 20c. The rotary axis 20 is combined to the cover of a notebook computer by a screw (not shown) fastened through the hole 20d. In this case, the housing 10 is similarly combined to the main body of the notebook computer by the fastening of a screw.
The torsion spring 30 is comprised of a plurality of clip type plate springs and is fixed to the housing 10 by being pressed to the rotary axis 20 and inserted to the axial hole 10a of the housing 10 together with the rotary axis 20.
FIG. 2 is a front view showing the friction hinge device of FIG. 1. As shown in FIG. 2, the torsion spring 30 is inserted to the axial hole 10a of the housing 10. The torsion spring 30 is fixed to the housing 10 not to be rotatable by fitting a lower projection part 30a of an arrow shape formed at the lower part thereof into the fixing slot lob of the housing 10. The rotary axis 20 is pushed to a central hole 30c of the torsion spring 30.
Meanwhile, two oil grooves 30b facing against each other are formed at the inner circumference of the central hole 30c of the torsion spring 30, and the lubricating oil is charged to the oil grooves. Therefore, it is possible to reduce the friction resistance generated between the outer circumference of the rotary axis 20 and the inner circumference of the central hole 30c of the torsion spring 30 during the rotation of the rotary axis 20.
In such a friction hinge device, if the rotary axis 20 is rotated (e.g., if the cover of a notebook computer is opened or the screen angle of an LCD monitor is adjusted), the rotary axis 20 receives the torque due to the function with the torsion spring 30, and thereby a rapid rotation is restrained to buffer the shock. Thereafter, when the rotation is stopped at a predetermined rotary angle, the rotary axis 20 is fixedly maintained at the angle by the pressure due to the tightening elasticity of the torsion spring 30. Since the torsion spring 30 is fixed to the housing 30 not to be rotatable, the generation of the torque due to the friction during the rotation of the rotary axis 20 is ensured. Since the torsion spring 30 of a closed circle shape stably supports the rotation of the rotary axis 20 and the friction resistance is reduced by the lubrication of oil, the rotation of the rotary axis 20 is smoothly performed.
However, in the conventional friction hinge device as described above, since the torsion spring is formed to be a closed circle shape, it requires much time and efforts to push the rotary axis 20 into the torsion spring 30.
Further, in the conventional friction hinge device, it is not that the whole sectional parts of the torsion spring 30 are contact with the rotary axis 20 but that only some parts of them are contact with the rotary axis 20. Since it is required a strong fastening elasticity of the spring when a predetermined torque is generated, an abnormal abrasion is generated due to the slackness and permanent transformation of the torsion spring 30 and the strong stress to the rotary axis 20, causing an unstable torque when it is used for a long time.
In addition, when the rotary spring 20 pushed into the torsion spring 30 is used for a long time, the force that holds the rotary axis 20 is deteriorated due to the abrasion of the torsion spring 30.